1. Field of the Invention
This invention relates to a semiconductor device and memory circuit system. For example, this invention relates to a semiconductor memory including MOS transistors having charge accumulation layers and control gates.
2. Description of the Related Art
In recent years, the demand for nonvolatile semiconductor memories with large capacity increases with the rapid popularization of digital cameras and mobile audio players. Further, NAND flash memories are widely used as the nonvolatile semiconductor memories.
With the above background, it is required to enhance the driving power of an output buffer of a semiconductor chip having nonvolatile semiconductor memories mounted thereon in order to transmit information of large capacity at high speed. The configuration of the output buffer is disclosed in Jpn. Pat. Appn. KOKOKU Publication No. H7-105151, for example.
When the driving power of the output buffer is low, the data transmission speed is lowered. However, if the driving power is made higher than necessary, there occurs a problem that the power consumption is increased and the operation becomes unstable due to overshoot and ringing of signal waveforms.